RICHMOND, Va.  An infestation of zebra mussels in a Virginia quarry has been eradicated, marking what biologists and environmental experts believe is the first successful extermination of the notoriously invasive species in open waters.

"I'm not aware of any other successful eradication," said zebra mussel expert Hugh MacIsaac, invasive species research chair at the Great Lakes Institute for Environmental Research in Ontario, Canada. "That's quite impressive."

The small black-and-white striped mussels, native to eastern Europe, were first discovered in Virginia in a quarry in August 2002, surprising and concerning state wildlife officials.

Zebra mussels are voracious eaters, gobbling up large amounts of plankton -- the same food many native freshwater fish need to survive. They also pose a threat to utility companies by clogging industrial pipes.

"Zebra mussels throughout North America and, in fact, throughout Europe, are a serious threat," said Ray Fernald, manager of nongame and environmental programs for the Virginia Department of Game and Inland Fisheries. "The economic and environmental damage that they can cause is tremendous."

A contractor, Aquatic Sciences L.P., of Orchard Park, New York, injected the quarry with thousands of gallons of potassium chloride solution over a three-week period beginning in late January. The eradication process cost about $365,000 (euro287,040), Fernald said.

The solution, while toxic to zebra mussels, did not pose a threat to the environment or humans, Fernald said, adding that water quality at the quarry and in nearby landowners' wells will be monitored for the next two years.

Zebra mussels were first discovered in the United States in 1988 in the Great Lakes, after apparently being carried in a trans-Atlantic ship's ballast water, which was emptied in the lakes. In addition to the five Great Lakes, the creatures have been found in 398 lakes nationwide, as far west as Kansas and as far south as Louisiana, according to the U.S. Geological Survey.

Amy Benson, a fisheries biologist with the U.S. Geological Survey, cautioned against celebrating too soon.

"You never know, they could be back next year," Benson said. "Mother nature has a way of surviving."